The present invention relates to weatherable films. More particularly, the present invention relates to such films comprising as one layer thereof a blend of polymers having exceptional stability to ultraviolet light degradation. The novel compositions of the invention are especially well suited for use as extruded films. Such extruded films may be employed as weatherable surface coatings to numerous substrates, especially steel in the form of sheets or other shapes for use in building panels or other architectural applications.
Accordingly, in one embodiment of the present invention, there is provided a film structure comprising an adhesive layer, an interlayer and a weatherable layer wherein the weatherable layer comprises the above polymer blend. In another embodiment of the invention, there is provided a unique laminated structure comprising a substrate having laminated thereto the above described weatherable film.
It is previously known in the art to employ chlorinated polyolefins in applications requiring weatherable surfaces such as in flashing and like architectural type materials. In U.S. Pat. No. 3,705,067, a flashing material comprising one or more film layers of an essentially non-plasticized thermoplastic sheet of solid chlorinated olefin polymer and an inherently porous woven reinforcing fiber mat is disclosed. No adhesive layer is provided. Contact between the fiber layer and the chlorinated olefin layer is obtained by application of heat and pressure. Blends of polyvinyl chloride and chlorinated polyethylene or other chlorinated polyolefins are also previously known. In U.S. Pat. No. 3,165,560, blends of polymers of vinyl chloride including copolymers thereof and chlorinated polyolefins are disclosed having improved impact strength. Foils and thin plates of such blends are further disclosed. Additional teachings of blends of polyvinyl chloride polymers or copolymers and chlorinated polyolefins especially chlorinated polyethylene are found in U.S. Pat. Nos. 3,006,889; 3,291,863; 3,299,182; 3,904,579; 3,940,456; 3,994,995; and 4,113,805. The teachings of all of the above identified patents are herein incorporated by reference.
In U.S. Pat. No. 3,845,166, there is provided a curable composition for wire insulation containing a chlorinated polyolefin, polyvinyl chloride, an ethylene polymer such as ethylene vinyl acetate and a curing agent.
While previously known blends have been usefully employed to prepare moldings and extruded objects, a coextruded film structure having an adhesive layer, an interlayer and a weather resistant layer of such blends is believed to be previously unknown.
It would be desirable to provide a coextruded film which is readily adherable to metal or other structural substrates having improved weathering characteristics. In particular, it would be desirable to provide a thin extruded film having properties suitable for use as a coating to a metal substrate.